A light emitting diode (LED) is a type of light emitting device capable of implementing light of various colors by utilizing various compound semiconductor materials such as GaAs, AlGaAs, GaN, InGaP, or the like.
Since LEDs have several advantages such as excellent monochromic peak wavelengths, excellent optical efficiency, compactness, environmental friendliness, low power consumption, and the like, they have commonly been applied to various devices such as TVs, computers, illumination devices, automobiles, and the like.
Recently, energy reduction initiatives have regulated the use of incandescent electric lamps, which are low-efficiency illumination devices. Thus, the replacement of incandescent electric lamps with high-efficiency illumination devices, such as an LED light emitting device, has been actively undertaken by light emitting device manufacturers and general illumination device manufacturers.
However, with a light emitting device, it is difficult to provide illumination having radiation characteristics similar to the light distribution characteristics of incandescent electric lamps, in terms of luminescent properties and a heat dissipation structure. Thus, recently developed light emitting device lamps do not have a wide light distribution angle due to the structural characteristics of the light emitting device in which light is only emitted from one side. Even when the shape of existing incandescent lamps is retained, illumination having a desired radiation form may not be realized.
In particular, an illumination area of a light emitting device lamp is small and the reverse side of a lamp cover, which is not illuminated, may be dark. Thus, research on a spherical light source having a radiation form such as that of an incandescent electric light bulb is under way.